It is furthermore claimed that if zombies are "conceivable" (a term over which battles are still being fought), then, purely from our knowledge of this "conceivability", we can deduce a priori that consciousness is extra-physical, in a sense to be described below.

Is that really the claim? Because it seems terribly silly.

Since it is conceivable (a pun, wait for it!) that Mommy fooled around on the Daddy who raised you, and you aren't his biological son, then the identity of your "social" father and your biological father can't be true in reality?

At bottom it seems like if two concepts are different, they're denying that in reality they're referring to the same thing. It's just odd.

It is conceivable that consciousness is something beyond brain function, but it is increasingly implausible.

And how about we turn around the proposition?

It is furthermore claimed that if non-zombies are "conceivable" (a term over which battles are still being fought), then, purely from our knowledge of this "conceivability", we can deduce a priori that consciousness is extra-subjective.